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do we plan to convert to a Combo Hybrid/Diesel boat? To see a diagram of the complete system, go here: Combo Hybrid/Diesel System Diagram First off... what is a Combo Hybrid/Diesel boat? This is when you have both an ICE (internal combustion engine) diesel, plus, you add an auxiliary electric propulsion system. Our choice to go with such combo propulsion system will spark the biggest debate on the outfitting of S/V Lynx. We know, because the debate about hybrids vs diesels is heated on the various boat forums out there, with the majority of the debaters touting the advantages of a diesel boat over electric hybrid. But what if you could have both in a combo system? Yes, there are some disadvantages as well as advantages, but for more about that, read on. The advantages of Electric Propulsion system: On the electric side, there are many advantages. So many, that for years we considered ditching the diesel engines completely. Some of these advantages are as follow. You have the peace and quiet of not hearing those engines rumbling. Then, there is the bliss of not breathing diesel fumes. When you have a large electric propulsion battery bank, you can also use it to run the air conditioning at night (without the noise and fumes of a generator running). We also save a of diesel fuel since we run between 3 and 6 hours a day off of electricity gained from solar. That makes for fewer trips to a fuel dock and far less times carting jerry cans of fuel from and to the boat by dinghy. Due to the large solar array to support those batteries, we also have an endless supply of electricity. That means, we can ditch using propane, which is mildly dangerous (explosive) and difficult to obtain in various locations, again requiring dinghy rides, adapters, etc. All of these things make an electric hybrid boat very attractive. Now the disadvantages of an Electric Propulsion system: It's expensive to install. In situations where you must motor for days on end, it is not as fuel efficient as ICE. And, finally, the electric motors are just not powerful enough in certain conditions (like a lee shore or a heavy current). So, those are some big problems! Thankfully, the solution is available, if you have the LCC (Load Carrying Capacity). You can keep the diesel engines and add the electric hybrid propulsion. So, let's look at the advantages and disadvantages of a combo propulsion system! The advantages of a Combo Hybrid/Diesel Propulsion system: You get all the advantages of a Hybrid (see above). You get rid of the disadvantages and can use the ICE system when it is needed. That won't be much of the time, but when it is needed, it could be a life saver! It is also the most fuel efficient setup, period (more on that below). Now, you might think it adds to maintenance costs, but that's not really true. There isn't much to maintain on the electric side (brushless motors have one moving part, a single bearing) and you should be running your diesels less often, cutting down on their maintenance schedule, so that's a positive! Finally, another advantage is redundancy. If you have ever tried to pilot a catamaran into a tight marina on one engine, you know how hard it is to accomplish! If one diesel or one electric pod are down, we still have a motor on each hull. Now the disadvantages of an Combo Hybrid/Diesel Propulsion system: There aren't many disadvantages, but let's get into the few that exist. First off, this system adds complexity to the boat since there are two propulsion systems. Secondly, it (may) add drag. Thirdly, it adds a huge cost to add the hybrid system. And finally, it also adds weight. Let's go into more detail about the negatives of a Combo Hybrid/Diesel. vs an ICE. 1) Complexity Well, there is no denying it, two systems are more complex than one. However, compared to an ICE equipped boat, becoming a Combo Hybrid/Diesel is not much additional complexity. Remember, you will already have batteries, alternators, inverters, MPPTs, solar panels, etc. Yes, you may add a few more of these, but the systems are already on board. So, what are you adding? Two things, a hydraulic lift system (and hydraulics have been around a long time on boats, you may have one on your auto pilot!). And you are adding the pod motors. Those have one moving part, a bearing. That is very little to worry about. So, really, we aren't adding much complexity. 2) Drag We are putting the two pods on fin shaped arms that can raise and lower out of the water at the touch of a button. This means when we are running on the diesel engines, they are not adding any drag to the boat. A side benefit is when we aren't using them, they aren't getting marine growth, burning through zincs, or just getting corroded. 3) High Cost to add the electric propulsion Well, that's an issue because it is really expensive, but not as bad as a pure hybrid boat. If we went pure hybrid, we would need four Oceanvolt ServoProps, which cost an insane $100,000. You need $2,000 worth of solar panels, about $13,000 worth of Lithium batteries (77 kw), $20,000 for a 20 kw generator, and there are a few other costs as well. Call it $130,000, minimum and with all the small extra things you need, it would top $140,000 installed. This is a reason why we recently abandoned Plan A, a straight hybrid boat. Even if we reduced to just two SD15 motors instead of four ServoProp SD15s, they would still cost $36,000. And then that hybrid system would be severally underpowered during an emergency, though it would be fine for normal uses. Even with just those two SD15s, we would still need the $20,000 20 kw generator, plus the $8,000 lithium batteries, and $2,000 worth of solar panels That totals $66,000. So, we came up with Plan B, the Combo Hybrid/Diesel. Because we don't need them for emergency power, we can go down to 7.5 kw pod motors. Dropping the power of the pods from 15 kw to 7.5 kw saves us nearly $16,000. With the lift arms and hydraulics added, it runs $20,000 total. We won't need the 20 kw generator, saving another $20,000. We do, however, need the batteries for $8,000 and the solar panels for $2,000. All total, this system is $30,000. Still, that's less than half the price of the Plan A system. OK, still too expensive? Not so fast. Perhaps it is better to say, there would be a large initial outlay of money. As we have shown (below), you will save fuel over time. How much? That entirely depends on your passages, how many, how far, and the cost of fuel. On our 142,000 nautical mile, meandering, double circumnavigations of the world, done over fifteen years, calculating every projected passage (which we have done, see 'Route'), we calculate that (at current average diesel prices, and assuming they don't go up), we save about $50,000 in fuel costs. We also save in other types of maintenance as well, due to using the generators and diesel engines far less hours. In addition, we save in propane, since we will convert everything to electric devices. For Plan A, we would save about $37,000 over the sixteen years. For Plan B, we save about $15,000 (more on why this is less, later). In total, for upgrading to the hybrid system, between fuel and maintenance savings we save $87,000 with Plan A for a net gain of $21,000. That's not bad. Or, even better, we achieve a net savings of $35,000 if we go with Plan B! Now we are talking! Note, this is assuming the price of diesel does not go up... if it does, then we save even more money on either plan. This is very likely over the 16 years, fuel prices are bound to go up. So, either Plan A or B both net us big savings in the long run, after paying off the price of the added systems. Also, don't forget that new technology always starts out expensive and then, typically, it goes down every couple of years and gets better at the same time. The cost to convert to a hybrid should drop over time. In the past 10 years, the cost of lithium batteries has dropped by 80%. If the past is any indication of technology and price, not too far into the future, the cost will be the same as diesels, and eventually become even cheaper. Regardless, even at today's prices, we calculate that going with the Hybrid of Plan A or, even better, the Combo Hybrid/Diesel of Plan B is worth the initial outlay of cost if you factor in the rising cost of diesel. However, with only a $30,000 outlay, Plan B is a much lower risk in case we are wrong about the amount of savings. 4) More Weight Regardless of whether we go with a Diesel , a Hybrid, or a Combo Hybrid/Diesel, we need the batteries and solar. So, that is not added weight. That means the only added weight is the pods, arms, and hydraulics. The pods only weight 41 lbs. each. If we add in the hydraulic motors, fluid, and lines, plus the fin arms to hold the pods, we get to no more than 200 lbs, total. For all the benefits we gain, we can live with that 200 lbs. Are we adding the hybrid propulsion to go Green? People have asked us if we plan
to go with a Hybrid/Diesel Combo system because we want a ‘green’ boat? The answer is, ‘no’. It’s
not that we don’t want to save our planet,
we just have other more selfish reasons for our choice in propulsion. We want the comforts that we get from an
electric propulsion system and the security of the power of
the diesels. However,
even though ‘going green’ is not our main reason for adding electric
propulsion to the ICE system, if
in
the pursuit of our comforts, we also
help put less CO2 into the air, we’ll take it. How
much? Well, that’s open to
debate. Making solar panels and Lithium
batteries require energy and
that generally adds CO2 into the atmosphere. How
much? Well, there have been
studies done on this. I found one such
study
on the making of solar panels that tells us it will take the first two
years of
service just to make back the energy that was used to make the panel. However, if the panel lasts for 10 years (or
more) then those other eight years are making carbon-free energy,
helping
reduce CO2 output. So, they will make us,
somewhat, green. But what about those Lithium
batteries? Again, a study was done on a 30
kWh car
battery that showed it would take three and a half years of a
gas-guzzling
vehicle, or more than 50,000 kilometers before the lithium car would
start
beating the gas car on carbon-dioxide emissions. Still,
eventually, it does save CO2. This means adding an electric pod
motor system will make
us a bit more green than
not doing so. We’ll take it. So, unless solar panels magically become far more productive (they won't, gains are in small percentages) and batteries become ten times more dense, you still have a problem. Now, if batteries became 60 times more dense, your range would be around 900 miles... that would be close to the range of most diesel boats. However, don't hold your breath on getting 60 times more dense batteries any time soon! Alternatively, if batteries became 20 times more dense, and you increased your bank to three times larger, you could about match a diesel boat's range, then recharge at port (or by sitting on anchor for a month!). This is slightly more feasible. You would eliminate the weight of the diesel motors and replace it with the weight of the additional batteries. However, without significantly increasing the output of solar panels (which isn't happening), getting a battery that is 20 times more energy dense than current lithium batteries is pretty useless. Thus, you still need a diesel generator for range and diesel engines for enough thrust (for emergencies) to make a hybrid a safe blue water boat. Conclusion, we aren't getting rid of diesel fuel anytime soon. Why not a bigger battery for the hybrid propulsion system? 65% use of a 38.4 kWh bank is about 25 kWh of the usable power without stressing the cells. That amount of power will motor us for about 3 hours at 5 knots. 5 kWh of solar gives us 25 kWh back a day, which takes us about 3 more hours motoring. That's fine for a trip that only requires that much motoring. However, on a long passage, you run into a problem. Your 5 kWh solar array can only recharge 25 kWh a day. Even if your batteries can hold 250 kWh, it would take ten days of sitting to recharge them and they would currently weigh 10,000 lbs! What about safety? Now, as to the question of safety. We can't go with electric propulsion because in certain situations, it may not be safe. The issue is, a reasonably powerful electric propulsion system that would equal 110 hp (twin 55 hp diesel motors, in our case) would require far too large a battery bank to power very large electric motors. 15 kw motors, like the Oceanvolt system, are really only going to add about 30 hp of power. You would need to go with four of these to have enough power. Therefore, you would need 77 kWh of battery storage. That 77 kw battery bank (which would have to be full at the moment of the emergency) would only power you for one hour at full thrust in all four motors. For longer than that, you would need two 30 kw diesel generators! Those are pretty large and expensive. All total, you are looking at a system that would cost something like $160,000 and weigh quite a bit, there would be over 1,200 lbs in just the batteries! It's much cheaper and more efficient (in terms of burning diesel in an emergency situation) to just have the 55 hp diesel motors when the $h!t hits the fan. However, if we just have the ICE, then we lose all the benefits of an electric propulsion boat (again, see above)! So, the best way for us to get all the comforts and fuel savings that an electric boat offers, yet still have the safety of decent power as well as efficient range from diesel engines, we plan to go with a combo system of twin 55 hp diesel engines plus two 7.5 kw electric pods, with around 38,400 kWh of batteries, and 5 kw of solar. So why not just go with the Hybrid? The Plan A Hybrid would not have enough power in emergency In the example voyages below, we will be calculating everything for Plan A off of two SD15 kw electric motors. The manufacturer claims these are near 40 hp diesels (but captains who installed them report they are closer to 30 hp). If you need more power you must go with larger electric motors or move up to four of this size. We don't want to do either of those choices due to the correspondingly larger battery bank, not to mention the high initial cost and added weight. Nor would we have enough solar panels to charge them back up in a day or two. Let's look at an example: one of the boats we are interested in comes with 40 hp diesels, but had the option to upgrade to 55 hp diesels. Most people opted to upgrade because they felt that 40 hp was underpowered for that yacht. If we went with two SD15 Oceanvolt motors, at 48 vdc, they are equivalent to 30 hp ICE. Therefore, our total available power would be 60 hp instead of 110 hp from the original diesels. That would make this boat severely underpowered. Most of the time, this would not matter since you rarely motor at full throttle. However, when you are caught in a bad situation more power is sometimes needed. Fighting a strong current come to mind, as does fighting off a lee shore during a heavy blow. We want enough horsepower for our boat to travel at a sustained 9 knots in those bad situations and two 15 kw electric motors will not supply that kind of power. However, for comparison sake, in the route examples below we will compare both a Plan A (Hybrid) and Plan B (Combo) against a pure diesel engine boat. The Two Hybrid Options (Plan A and B): Plan A: Two Oceanvolt SD 15 kw motors and a 20 kw generator: In this case, the boat's propulsion system would consist of two SD15 motors using a Gori three blade folding propellers and a 38,400 kWh battery bank backed up by two generators, one 20 kw and one 10 kw. We don't need the servo prop models for our boat. The fact is, we aren't buying a performance catamaran. If we were, things would be different. We might have less room for solar panels and the boat would average higher speeds. Therefore, regeneration would be much more efficient and desirable. But for our boat, that won't be true as our average speed will be more like 7 knots instead of 10. Example, an SD15 ServoProp generates 1 kw at about 8 knots, but 2 kw at 10 knots. With our boat, we won't be going much more than 8 knots all that often, and 6 or 7 knots a lot of the time. Therefore, regeneration isn't that advantageous. Add in the fact that regeneration slows the boat down by at least half a knot per motor, so you would only want to use it when the boat is sailing at fast speeds. On a production boat, like we plan to use, you will find that you won't want to use regeneration all that often. And, on the days where the wind is blowing strongly enough for good regeneration, we won't need the energy to motor anyway, since there is plenty of wind to sail. So, based on this, it works out better to buy two SD15 motors (the non-servo prop model) using Gori folding props. This would cut down on the electric motor's computer aided complexity and cost less if we happened to hit something with a brass prop vs. computer controlled blades. Not to mention, the SD15s are cheaper than the ServoProps by $7,000 per motor. Plan B: Stick with the existing diesels and add two 7.5 kw pod motors: So, more data came through from two of the boats using Oceanvolt motors, and they listed a couple of issues. One boat was struck by lightning and lost all propulsive power since they were a purely electric propulsion boat. The other boat quit their circumnavigation because they were not generating enough power through regeneration. Let's start with that second boat. They only had 2 kw of solar panels and no generator. Those were both mistakes, in our opinion. Based on the numbers we ran, you need about 5 kw of solar and a good size diesel generator to extend your range plus a smaller backup generator for safety. However, this boat also reported only getting about 30 hp equivalence with their SD15 motors. That is a bit underpowered for our 46' catamaran, which really would work best with two 55 hp motors. Based on their regeneration numbers and reports on low amounts of horsepower, we had to think twice about that being our main propulsion system. Now let's talk about the first boat that was hit by lightning. They had originally gone with the four SD15 motor configuration to get enough horsepower for their large cat. They did report that his was overkill for most situations, as two would get them by for normal motoring. However, after being struck by lightning, they decided to get rid of two of their four SD15 motors and install two diesel engines. Now they can motor off of their two SD15s when they want to, but have the diesel engines as backup for longer range when extended motoring is needed. Also, in an emergency, they will have more power. Finally, the diesel engines act as a backup to the electric motors if their boat is struck by lightning again. So, based on the information gained from these two boats, we got out our pen and paper again and ran some numbers. We found two 7.5 kw, 48v, electric pod motors that run at higher RPMs (2,500). If we ditch the SD15 motors and, instead, add these two smaller electric motors, yet keep the existing diesel engines while added two high power alternators (one for each diesel engine) we could have the benefits of both systems. This configuration will allow us to get almost all the benefits of the electric drive system. We could still motor at 5 knots on electric for about 3 hours sending 3.75 kw to each pod motor from the initial charge on the batteries. Plus, we would get another 3 hours of motoring from solar recharge during a sunny day. That is a total of 6 hours per single sunny trip, which would generally be plenty of motoring time, since we are a sailboat. However, those two 7.5 kw pod motors are nowhere near strong enough to deal with an emergency, like a stiff current or lee shore in a strong wind. However, we would still have the full power of the 55 hp diesels to add to the pod motors when needed. If we get hit by lightning, we still have the diesels. As for other times, like entering and leaving port, we have the electric motors, which are better for maneuvering and don't need to be warmed up in the morning. They are also useful for some regen, when the wind is blowing strongly, or for motor sailing, or drogue effects, etc. And, we still have big enough battery bank for air conditioning all night, if needed. Finally, there are significant fuel savings in this configuration (see example passages, below). Below is a comparison of passages on Diesel Boat vs a Hybrid (Plan A) or Hybrid/Diesel (Plan B). I'm going to hit the highlights, as we see it, and show you why we are considering making the change to add electric motors to the ICE already on board. The comparison comes down to these two main factors. 1) On the diesel side: Firstly, diesel engines are far cheaper than setting up a hybrid and come with the boat! Secondly, diesel engines turning a prop are anywhere from 10% to 20% more efficient than a generator supplying electric power to a motor turning a prop. Why the percentage range? It depends on the number of conversions of energy. If you go directly from a diesel generator, without going to the batteries first, you cut down on some of the conversions. Hence, there is not as much of a penalty. At the root, the extra cost of the system, the percentage loss of power, and the overall extra horsepower are the main factors which most proponents of diesel power will use to argue against a Hybrid system. And, they are correct about these factors! However, as you will see, this isn't the whole story, there are many advantages for an electric propulsion system as well. 2) On the hybrid or combination side: The electric system obtains energy from several sources, diesel fuel (generator or engines), solar power, wind generators, and some from sailing regeneration (more on what this is later and why is isn't a significant amount). Let's talk about solar first since it is the big one. A catamaran comes with a large surface area over the salon and cockpit. If you also add on a stern arch (which we plan to do, see photoshopped image at the bottom of the page), specifically designed to hold more solar panels, it is possible to add around 5 kWh of solar panels to a boat like the Salina 48 or Leopard 48. Without enough solar, an electric/diesel boat is not as viable for saving fuel. Now, some people tell you that your panels will receive about 4 hours of their full rated maximum over a typical day, but we have obtained real world numbers from several cruising boats who tracked their charge rates over time. For example, one boat has 930 watts of solar and gets about 5 kWh a day from that into the batteries (while in the tropics). That means, on a typical sunny day, on a boat with 5 kWh panels, we will supply about 24 to 25 kWh of energy back into our batteries. This does not take you quite as far as you might imagine, in fact, 25 kWh will only last for about 3 hours of motoring at 5 knots (more on that below). Here are the passage examples that I will use: 1) Short passages of less than 6 hours. 2) Single day passages during daylight, going 60 miles. 3) Single day passages during night, going 60 miles. 4) Single day passages during daylight, going 90 miles. 5) Two day passages with two days of sunlight, going 260 miles. 6) 21 day passages across an ocean, with steady trade winds, going 3,024 miles. 7) 21 day passages across an ocean, with steady trade winds, crossing the equator, going 3,024 miles. 8) 21 day passages across an ocean, becalmed in the middle for a week, going 3,024 miles. For comparison sake in these examples, here are the boats we are using (this data comes from captains on real boats): 1) For the diesel boat we are using a 46' catamaran, fitted with 54 hp diesels. With one engine running they reported burning only a half-gallon an hour at 5 knots. That's good fuel economy! Some cats report more like 3/4 of a galleon an hour. However, we'll go with this more efficient number to give the diesel boat its best numbers. 2) For the Plan A hybrid, we are also using a 46' catamaran equipped with the Oceanvolt SD15 motors and Gori 3 blade folding props. At 5 knots they used 3.75 kw of power, each. Unlike the diesel, you need to run both SD15 motors, so the total consumption was 7.5 kw. 3) For the Plan B hybrid, we will still use a 46' catamaran equipped with two 7.5 kw electric pod motors and two 55 hp diesel engines. The pods will still use 3.75 kw of power, each, or 7.5 kw total to push the boat at 5 knots. Note: I'm getting numbers on the OV motors from two real world sources. One captain's boat has one SD15 ServoProp and one SD15 with a Gori propeller. He reports that the SD15 with the Gori prop uses, and I quote, 'half the electricity at the same revolutions then the ServoProp'. The other captain is running two SD15 ServoProps and reports that running at 7 knots he uses 7.5 kw per SD15 ServoProps, 15 kw for both. Now, for our fuel comparisons I am reducing the speed of our catamaran to 5 knots, this will drop our ServoProp consumption numbers down to 3.75 kw for each motor, or 7.5 total. However, we know from the other captain that you only use half that power with the SD15s using a Gori prop. So, the total required output would be 3.75 kw. However, just for arguments sake, let's assume it is the same efficiency as the ServoProp. That means 15 kw (total) gets you 7 knots. Reducing to half speed (3.5 knots) would reduce your power requirement by 8, so about 2 kw. But, if we only reduce from 7 knots to 5 knots, that should require about 7.5 kw (total). To get that number, I am using the standard calculation of the required propulsive power increasing to the cube of the speed. This means that to double your speed requires eight times as much power. Or reducing your speed by half only requires 1/8 the power. So, reducing from 7 knots to 5 knots, all total, the motors use 7.5 kw to move at 5 knots. This means, for a battery bank of 38.4 kWh, with a usable 25 kw, you can motor for just about 3 hours (22.5 kWh) leaving 2.5 kWh for house needs. That jives with the stats from another catamaran using a new Volvo electric sail drive motor. They state that it travels 27 NM @ 5 knots on a 40 kWh battery. They are probably only using 80% DOD. That would make their consumption about 7.4 kw. So, that is about the same, around 7.5 kw (3.75 per motor) to motor at 5 knots which confirms our numbers. For the primary generator on Plan A, we're using a 20 kw DC generator, which burns 1.6 gallons of fuel when outputting its maximum 20 kw of power. However, figure a 20% conversion loss on generated power. The example cat will be equipped with a 38.4 kWh battery bank, allowing for 25 kWh usable Lithium batter discharge (about 65% if we keep the charge level between 20% and 85% to make the batteries last longer). For the Plan B Hybrid, we add high output 48v alternators that put out 100A, or about 4.5 kw per hour, per motor running (again, losing 5% when sending that power to the batteries). We'll figure .75 gallons an hour for a 55 hp diesel engine. I am also using the 50% motoring rule, which means you sail 50% on a typical trip and motor the other 50%. This data is gathered from many different captains. Note, I am not figuring in any regeneration from sailing with the props turning backwards in these examples since this is only viable on very windy days or it slows the boat down too much and, therefore, doesn't really save much fuel. |
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Example One:
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Diesel Boat has Greater Range Myth: One thing we keep reading from forums or hearing on Youtube videos is that diesels have greater range than a hybrid electric or combo electric/diesel boat due to the diesel fuel being more energy dense and conversion losses in an electric hybrid system. This is just not true, assuming you use a large enough solar array. Let's use the same 48' cat with 55 hp diesels against our Hybrid or Combo options. 1) Diesel Boat: Let’s say your boat has a 100 gallons fuel tank and uses 0.75 gallons an hour at 5 knots. That means the diesel boat can motor for 133 hours, or 666 nautical miles. 2) Hybrid Boat, Plan A: The first day we get a free 3 hours of motoring (about 15 miles) plus 15 from solar recharge. Each additional day we get 3 hours of motoring from solar recharge of the batteries, for another 15 miles. The two electric motors use a total of 7.5 kw to push the boat at 5 knots. You have to run the generator for 2.5 hours to recharge the battery bank (7.5 kw goes to the motors and 10 kWh gets stored in the batteries). This will recoup the 25 kWh you used from the batteries. During that recharge time you travel 12.5 nautical miles. Then, you get to motor for 3 hours off of the recharged batteries, going and additional 15 nautical miles without the generator running. So, about every 5.5 hours, you travel about 27.5 miles and burn about 4 gallons of diesel. Converting this to a day, you use about 17.44 gallons a day to travel 120 miles. With 100 gallons you go about 5.75 days before running out diesel. Of course, you also get to add the extra 12.5 miles from solar each day, going an additional 72 miles during that period. Finally, add the initial 30 miles you went on batteries the first day. All total, you travel about 792 miles, about 126 miles more than the pure diesel boat on the same amount of diesel fuel. 3) Combo Boat, Plan B: With our diesel engine/electric pod hybrid, things are even more interesting. Each day we get 3 hours of pod motoring from solar recharge. Then, we use a single diesel engine for about 6 six hours and recharge the battery bank (and add some energy for House needs) and then motor for 3 hours on batteries. So, each day we use the diesel engines about 16 hours, burning 12 gallons of fuel. If we divide that into the 100 gallons the example boat carries, we get just over 8 days. At 5 knots, you travel 120 nautical miles a day, so we go 960 miles before we run out of fuel. As you can see, our range from a Plan B boat is far more! This is due to recharging batteries from solar and while motoring we use the more efficient diesel engine (compared to loses with a generator system). This is not a surprise, we get the best fuel mileage advantages of a diesel boat and the best advantages of an electric boat. (NOTE: this does not factor in added weight of 850 lbs for the electric system, so that may lower this fuel savings a bit). However, we're not a motor boat, we're a
Hybrid sailing boat! In either Plan A or B, if we only have to motor for 3 hours a day while sailing the rest, our range is unlimited since we get that from solar recharge. The diesel boat will, eventually, run out of fuel. This is not perpetual motion, we are gaining fuel from the sun. What about extended stays in areas with no fuel stations? This is even more advantageous to the hybrid or combo boat. On these electric boats, time equals fuel. Every time you sit in some atoll, enjoying your long stay, your batteries are being filled by solar power, in essence, refueling your boat. Diesels get no additional fuel in these remote locations. On a Hybrid, your range and, therefore, time in these remote areas is extended to as long as you have food to eat. You can even keep moving from island to island. Your range is vastly extended by free solar 'fuel' for propulsion or House needs. You should stick with diesel only because diesel fuel is more energy dense! We
were recently reading a discussion on a forum where one poster
was attacking a diesel/electric hybrid system. One of his many
flawed
arguments was, instead of adding the weight of those heavy batteries,
we should just add more diesel storage and get more range since diesel
fuel
is far more energy dense than batteries. His statement is
correct but
he is missing the entire point. He is making the false assumption
that our goal is range at any cost. A different goal would be to
have
increased range without burning more fuel. This is absolutely
possible
with a hybrid diesel/electric boat. If you lift the electric pod
motors, thus causing no additional drag while using the diesel motors,
you only lose a tiny bit of range due to the added weight of the
batteries (and any other components of the electric propulsion
system). However when you have power in your batteries from
precharging them with solar, and gain additional solar power each day
while
sailing, you add range without burning more diesel fuel. However,
that
is not our goal! Our goal is to use less diesel fuel while
sailing
around the world. We easily achieve that goal with a hybrid
diesel/electric boat (see example trips above). So, as you can see, the ‘diesel has greater range’ is a myth. All it takes for a Plan A or B boats to exceed the range of a diesel boat using the same amount of fuel is sufficient solar panels on board. We can go further and say we will burn less diesel fuel over the long run. In our case, we plan the same 5 kWh total from our panels as in these examples. As for the Plan B hybrid, it just has greater range than either of the other two options since it has the advantages of both the diesel boat and a hybrid boat! |
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| Regeneration What we are talking about here is letting the props turn backwards as the water moves past, generating power back into the batteries. In essence, turning wind power (on the sails) into electricity stored in the batteries. Using the Oceanvolt ServoProp system, you could expect to get about 1 kWh per motor while sailing at about 8 knots. This is slightly above the average sailing speed for our type of comfortable catamaran (see chart below for how much regeneration at what speed). So what is the issue? Well, each motor will slow the boat by a half knot, so that's a full knot if both props are used to regenerate! There is no free lunch. A full knot means that over a long passage of something like 21 days, if you regenerate, for say, 12 hours a day, it means you lose a knot per hour over 12 hours, or nearly 14 miles of travel a day. When you multiply that times 21 days, that's 294 miles. That equals another two full days of sailing time added to your passage! If you figure you must motor for half of those two extra days, you burn fuel. |
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| But,
not so fast. There are some ways to make regeneration more
efficient. One is
to only regenerate while your boat has enough wind to take it over
efficient hull
speed (the speed in which your boat now requires more energy to gain
the same increase in speed). Example: If your boat sails at 5
knots in 10 knots of wind, and 8 knots in 16 knots of wind, but
suddenly requires 24 knots of wind to go 10 knots of speed (no longer
achieving half of wind speed), your efficient hull speed is something
just over 8 knots. This means that, once you have enough wind to push your boat over 8 knots of hull speed, and you choose to regenerate, there is likely enough wind to keep you sailing at that same 8 knots (hull speed). Basically, you are wasting some of that wind energy trying to push your boat beyond your efficient hull speed. So, instead, you could spend that wind power on regeneration. However, this means you will only be regenerating while the wind is blowing something like 20 knots or more (in this boat's hull speed example). That doesn't happen all that much on a typical trade wind passage, especially with a slower production catamaran. However, if you only regenerate during these periods of strong wind, you won't likely add much more time to your trip, yet you will regenerate (and, possibly, at even more than the 1 kw/motor gain). However, remember, if the wind is blowing strongly enough to use regeneration, it is also blowing strongly enough to sail and not be motoring. Therefore, you aren't using energy sent to the motors and don't need that regeneration power since the solar panels will do the job to keep up the house uses and recharge the batteries to full anyway. You might as well just sail slightly faster. Due to this, we don't really plan to use regeneration very often. If we are sailing in strong winds and the batteries are low, we might do it then, but when the batteries are charged up, why bother? Slowing Down There are times when you want to reach a destination at a specific hour, like morning, as the sun is rising. Getting there too soon means entering in the dark. If the wind comes up too much, on a diesel boat, you would have to reduce sail to slow down. However, in the case of an electric boat (Plan A or B), we could chose to use one or both electric motors in regeneration mode to slow us down slightly while leaving the sails up. If that's still not enough speed reduction, we reduce some sail, yet keep regenerating. The added benefit here is that we get a little power regeneration while we slow down to arrive at the right time. This also works well with a standard SD15 or any other electric propulsion that allows regeneration (you don't need the ServoProp motors for this benefit). |
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| Drogue effect: Another advantage to regeneration, especially when sailing on a catamaran, is the drogue effect. In bigger seas, as you surf down the face of a swell, catamarans can pick up too much speed and then their bows pierce into the face of the next swell. Often, catamarans will deploy a drogue to slow them down. If you put both of your electric motors into regeneration mode, with just the right amount of forward throttle, they will slow you down a knot as the boat surfs down the wave, however, as the boat starts to climb the next face, the motors will power you up. This effect evens out the speed of the boat, somewhat, making for a slightly more comfortable ride. Note: if you are still surfing too swiftly down a wave, add a drogue. We plan to go one of the adjustable models so we can tailor the drogue effect work with the electric motor drag. |
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| Motor Sailing While sailing we also have the option of motor sailing. This is a bit different than a diesel boat motor sailing. Typically, on a diesel boat, once the wind drops to the point where you are only going 3 or 4 knots, most sailors take down their sails and just motor at 5-6 knots. The reason is simple, the wind isn't going to help them anymore if the diesels are pushing you at 5 knots and you don't want to run a diesel at a low RPM. That is bad for the diesel and isn't going to save you much fuel anyway. You might as well put them at their optimum fuel efficient RPM and do that 5-6 knots. Motor sailing with an electric motor is different. Electric motors have full torque at any RPM. Therefore, depending on the wind angle, you can just give the electric motors a little power and add, say, 1 or 2 knots to your boat speed, while continuing to sail. At that low of a power draw, our battery bank can go for something like 24 hours. Now you can keep the sails up, adding a knot or two to the motoring speed, getting you to 3 or 4 knots of total speed, without burning diesel fuel. |
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| Wind Generators These are small turbines on a pole, driven by props turned by the wind. At maximum rated power, they seem like a pretty good choice for making power, but not so fast. First off, you can't trust the manufacturer's numbers. They use a constant stream of wind in a wind tunnel, you probably won't see those same numbers in the real world where the wind is more fickle. Secondly, those maximum power numbers are for high winds. For example, in the chart (below) you can see that at 20kt of wind the various manufacturer's models listed output between 140-280 watts per hour. However, if you are a cruiser circumnavigating the world (like us), and typically going down wind with the trade winds, then seeking sheltered anchorages out of the wind, you aren't going to see a lot of days with that kind of sustained wind. On average, you're more likely going to be down in the 1 to 12 knot category. Even at 12 knots, the output is only 20-55 watts and below 4 - 6.8 knots of wind you aren't getting any. So, you are only going to see a small amount of energy gain most of the time. A single 330 watt soler panel is going to gain a kilowatt in the five hours it is in sunlight, just about matching what a wind generator will output in 24 hours in 12 knots of sustained wind. If you don't have room for more solar, a wind generator could make some sense. But, don't forget, wind generators do make noise as they turn, there is a slight danger of spinning blades, and they require eventual maintenance since they have moving parts. There is also a significant cost to buy one. After considering all this, we haven't yet decided if we want one or even two wind generators on board. If you think about all the days of less than 12 knots of wind, overall, we will gain more power from a additional solar panel than from a wind generator, with no noise. Sure, there will be days when the sun is blocked yet there is significant wind, and we won't get that solar power, but the number of those days are infrequent, so in those cases we could just run the 20 kw generator for a short period. Example: if the wind is blowing at 20 knots, a typical amount of gain from the wind generator is 200 kw, or 4.8 kWh in a 24 hour period. We can run the generator for fifteen minutes and get the same thing. That is only fifteen minutes of generator noise, then quiet, or 24 hours of hearing those turbine blades. Yes, that costs us about a half gallon of fuel, but we won't have to do that very often and at a savings of a half galleon of fuel only per time, it would take something like 700 days of doing this to repay the price of buying the wind generator! We'll look into this further before making a final decision on one or more wind generators, but as of now, we're leaning toward skipping these on S/V Lynx. |
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| Diesel vs Hybrid, vs Combo Hybrid/Diesel Conclusion: To quote a boat owner who has sailed their cat around the world for five years, he stated, "The single most important thing on our boat is power. You cannot have enough." Or, another boat owner who said, "We have a very large battery bank, large enough to run the air conditioning for half the night." Their battery bank is less than 10 kw. With 25 kWh of usable power from the 38,400 bank, we can run our air conditioners all night, silently, and recharge the batteries in the morning when we don't disturb our current neighbors by running a diesel generator at night. All total, over all passages we make on our epic voyage, we could save over 11,000 gallons of fuel (this is a rough estimate, using the two leopard boat numbers, though our boat will be slightly different. That’s the estimate on how many gallons we save using a combo boat over a diesel engine only cat on our particular double circumnavigation voyage. You also get rid of all the costs, dangers, and hassles of propane, since you are an electric boat, you use all electric appliances, no propane. So, no time carting the empty bottles ashore, finding a compatible fill nozzle, going back to pick them up later (in many cases) and paying for propane. However, currently, the cost to upgrade to a Plan A hybrid boat is too steep! It will take more nearly 10 to 16 years to recoup the initial expenditure (depending on if and how much diesel goes up). Fortunately, the Plan B option is much less initial expenditure ($37,000 less). Therefore, we could recoup that expenditure in more like 4-6 years and eventually save money over a purely diesel boat. But is it worth the $30,000
initial outlays of cash? Yes! Here is why. Comfort! Here are the comforts we get by having the electric system on board (batteries, solar, etc.): 1)
We will be able to run our air-conditioning,
all night, while we are anchored in a hot and humid place, without
turning on the
generator. 2) The extra stored energy means we can make more water and, therefore, take more showers. 3) During
our double circumnavigation, we
save endless time and energy in not having to, find, cart, pour, and
filter over 1000
jerry cans of
diesel fuel into our tanks. 4) We save 23,000 hours of not smelling exhaust. 5)
We save the same 23,000 hours of having to listen to a
diesel engine. 6) We are
more self-sufficient, able to remain away from civilization for longer,
without needing diesel. 7) We’ll spend less time going to fuel docks. 8) We spend no time searching to find or fill propane bottles. 9)We
spend less time
doing
maintenance on diesel engines and sail drives (mostly due to running
the generator or diesels a lot less hours, so maintenance cycles are
further apart). 10) We can motor sail (silently). 11) We can use regeneration for a drogue effect to even out the motion of the boat. 12)We
have instant power at any time without warming up the diesels.
This is good in port, and may help to complete a tack. Even if
the pods are raised, it takes less than 20 seconds to put them in the
water with the hydraulic system we are adding. 13) We save time and fuel not having to warm up two diesel engines every time we leave port. 14)
We have more power for charging all our toys. So, how do you put a price on
comfort? If
we have to cough up $30,000 extra to refit the boat for Plan B... so be
it! Most, if not all, of that initial
coast will be regained in the first 5 years and we will save money in
the long run.
However, we expect prices to come
down in the next three years, so maybe this initial cost will become a
bit less. Comparing the two Hybrid Plans,
Plan B has far less initial cash outlay and saves more money in the
long run. On the downside, it adds weight to the boat. Then there is the safety
issue. When it comes to safety concerns,
the Plan B boat wins, hands down. After all, it has two separate
propulsion systems which combine to have more power than the
diesels and far more than the Hybrid Plan A. It is also safer if
we
are hit by lightning. On the down side, the Plan B boat has more
maintenance costs (one additional diesel, since it has two engines and
a generator vs two generators). It also has two sail drives that
need
serving. So, currently; based on the
comforts
gained, safety, and cost, Plan B is the route we will choose to go
during our
refit of S/V Lynx. However, here are the two system setups (Plan
A and Plan B): |
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| The Plan A Hybrid Setup for S/V Lynx (this
is now our 2nd choice; see Plan B below for our 1st) |
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| 1) Two Oceanvolt SD15 electric
sail drive motors with Gori props: Oceanvolt SD15 Synchronous permanent magnet electric motor. Sail Drive with 1.93:1 reduction. Lightweight: weighs as little as 42.5kg (motor & sail drive). The only complete electric inboard propulsion system with EMC certified closed circulation liquid cooling providing both cooling and lubrication. Functions as a hydro generator to generate power while under sail. Gori three blade folding prop: We wold go with a couple these with a Gori folding prop, to quote their site, "The 3-blade Gori folding propeller marks a technological and functional leap forward in the development of propellers for sailboats. It is now possible for sailboats and motorsailers to gain the folding propeller's speed advantages under sail, combined with the fixed propeller's thrust capability when motoring. The 3-blade Gori folding propeller was introduced on the market in 1994 and won the DAME award and HISWA award the same year, as the best new marine product. "OVERDRIVE" FUNCTION The 3-blade Gori folding propeller's "overdrive" function adds a new dimension to sailing under power. The helmsman can choose the propeller pitch and profile in the water while sailing forward, by regulating the yacht's shift and throttle control. Without the use of vulnerable hydraulics or complicated mechanical devices. The "overdrive" is used when motorsailing in fair weather or when using the engine under sail. The "overdrive" gives the same speed at lower rpms. The result is less engine noise, less vibration and better fuel economy." |
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| 2) 38,400 kWh lithium battery bank: This number isn't random. The typical amount of energy we could recoup in a day of good sunlight is 25 kWh which is also the usable power from this size bank, if we keep the batteries between 20% and 85% charge. With a single sunny day at anchor, we can net 25 kWh of solar, which refills our bank completely. Assuming we are using power for a lot of house needs, certainly in 2 days we can recoup a full battery charge for the next voyage using just solar regeneration. |
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| 3) Five kilowatts of solar panels: Solar panels are critical to the Hybrid system being viable. You must regain a lot of power from the sun or you are just burning diesel up through a less efficient generator. To that end, if we go with a Salina 48 or Leopard 46, we plan to build a special stern arch. This will extend the coach roof line. We are also adding a hard top over the helm, which will add a little more space for solar panels. These are being added to increase our total solar panel array. On the Salina 48, we can get to over 5 kw. On the right are two photoshopped images of a Salina 48, showing the arch we plan to add to the stern. This arch will not increase the length of the boat, since it ends at the same distance out as the sugar scoops. To keep the weight down, we plan to build this out of carbon fiber. We will also squeeze in panels on the regular coach roof and Helm roof. |
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| 4) One 20 kw and One 10 kw (or slightly
smaller) Diesel Generators: The 20 kw (closer pic to the right) is the main workhorse, which can push the boat to 7.5 knots, running both SD15 motors if needed or supply power to the battery bank as well as the motors when running at 6 knots or less. This generator weighs 320 lbs. As a backup, there will be a lighter 10 kw generator (farther pic to the right), capable of sending 5 kw to each motor to push the boat at 4 knots or, while at anchor, we can run this generator to recharge the batteries or run the A/C saving some fuel since we don't need the power of the big 20 kw generator. This generator weighs a maximum of 260 pounds if we go with the 10 kw generator. (We hope the boat we buy comes with the smaller generator already). In an extreme emergency, after battery power is exhausted, we can run both electric motors at maximum thrust by running both generators at the same time, giving us 30 kw, supplying 15 kw to each of the two SD 15 motors. They can then run, flat out, for as long as the diesel fuel holds up. |
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| 5) Diesel Fuel tanks We plan to keep the existing diesel fuel tanks, (127 gallons on the Salina 48, 185 gallons on the Leopard 48, and 248 gallons on the Saona 47). Most of the time these will be kept fairly empty, holding perhaps 50 gallons of diesel for emergencies since most of the time we will run without any diesel usage at all. However, when facing a long passage, or a long time away from civilization, we can top off the tanks. Sailing with just 50 gallons of diesel saves a lot of weight! On the Salina 48 it saves us 539 lbs, on the Leopard 48 is saves 945 lbs, and on the Saona 47 it saves us 1386 lbs.! The two generators plus the batteries and SD 15 weigh a total of 1095 lbs. Or, if you look at the Salina 48, after removing the diesel engines and sail drives, and reducing to 50 gallons of diesel, even with the entire hybrid system on board the boat weighs 339 pounds less, the Leopard 48 weighs 745 lbs less and the Saona weighs 1186 lbs less! |
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| The Plan B Hybrid Setup for S/V Lynx (and
our current top choice) |
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| PROPULSION: Two Aziprop 7.5 kw Fischer Panda Pod motors 2500 rpm 28 Nm 48 volt 18.7 kg (41pounds) These electric pod motors will be used for the majority of our propulsion needs. Here are examples: 1) When entering or exiting port, or moving around an anchorage. They don't have to be warmed up, are virtually silent, and have excellent low speed properties since electric motors have full torque at zero RPM. 2) During a passage when we want to motor sail. They put out no fumes are virtually silent, and at low power usage can go for a very long time on batteries. 3) For limited motoring when the wind drops (up to about 3 hours). 4) For regeneration, drogue, and just slowing us down (on purpose), on some occasions. To cut drag, these pod motors will be mounted on arms that are raised with a hydraulic motor. Here is a link to a video showing a system that does this (these are no longer sold though, but we will make a similar system). https://www.youtube.com/watch?v=nl1a_ACQmvs Two Yanmar or Volvo 55 hp diesel engines These engines will come with the boat. These will rarely be used compared to the electric pod motors. We plan to use the diesel engines for three purposes: 1) On a long passage where we must motor for more than three hours, continuously, as the diesels are more efficient in fuel use than a generator supplying power to an electric motor. 2) To heat water and charge batteries using a High Output alternator while motoring. (100 ah at 48 volt, one on each engine) 3) In emergencies, when high power and thrust are needed, like when fighting a current or in a large blow with a lee shore. FlexoFold three blade folding prop: When it comes to the diesels, based on reviews and tests, we plan to use Flexofold 3-Blade sail drive Folding propellers. The strengths of these props are as follows: 1) Low drag: Compared to fixed props, these folding props increase the sailing speed of the boat by 1 to 2 knots (since there are two of these in the water all the time). 2) Maximum Speed: They are the highest rated for speed of all the folding and feathering props we have seen in tests, up to a knot faster than the competition. (See test result below) 3) Pulling power in forward (bollard test): Again, they achieved top marks in this test, which means when we are fighting a headwind, going against a current, etc, these pull the boat forward better than other options. (See test result below) 4) Simple: Compared to feathering props, these are simpler to maintain and have less cost in rebuilds. To the right are the 2015 Yachting Monthly posted results from their tests on speed and bollard pull ahead: Note, though stopping power wasn't as good as some of the other props, that is not as much of an issue with our boat since we also have two electric pod motors to aid in bringing the boat to a stop when needed. On folding props: Though we were interested in the Gori props, research shows that using them on a sail drive is hard on the transmission if you try to use their 'overdrive' feature, which requires you to go from reverse to forward without stopping in neutral first. With the electric drives this was less of a concern. Also, though there have been reports of both Gori and Flexofold props coming off in rare cases, the Flexofolds have more mechanisms for keeping the prop on the shaft where the Gori props only have two, tightening the bolt and using loctite. The Flexofolds have these two methods plus a metal tab washer with a nut and bolt system that bends the metal washer to keep either the bolt or the separate nut from backing out. |
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| 2) 38.4 kWh lithium battery bank: (800ah at
48volts) This number isn't random. The typical amount of energy we could recoup from solar in a day of good sunlight is 25 kWh, so recharging a 38.4 kWh 70% is very doable since you won't ever completely deplete it. In just one sunny days at anchor, netting 25 kWh of solar, we can recharge and are good to go. However, with House needs, we will often spend two days at anchor before any long passage or use the generator for a short time to top off the batteries. But, when we have time, in 2 days we can recoup a full battery charge for the next voyage using just solar regeneration. We have not settled on exactly which batteries we will buy yet, but are leaning toward LifePO4, DIY option (see Solar and Batteries). But, we are hoping for better choices in the next couple of years as battery technology changes and prices continue go down (hopefully). |
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| 3) Five kilowatts of solar panels: Solar panels are critical to the Hybrid system being viable. You must regain a lot of power from the sun or you are just burning diesel up through a less efficient generator. To that end, if we go with a Salina 48 or Leopard 46, we plan to build a special stern arch. This will extend the coach roof line. We are also adding a hard top over the helm, which will add a little more space for solar panels. These are being added to increase our total solar panel array. On the Salina 48, we can get slightly more than 5 kw. On the right are two photoshopped images of a Salina 48, showing the arch we plan to add to the stern. This arch will not increase the length of the boat, since it ends at the same distance out as the sugar scoops. We will also squeeze in panels on the regular coach roof and Helm roof (see image, right). NOTE: even though the original sun deck is shown in these images, if we go with a Salina 48 we plan to remove that deck completely and add a different dinghy lift system. |
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| 4) One 10 kw (or slightly
smaller) Diesel Generator: Our 9 - 10 kw generator is for use while we are at anchor if we run out of battery power. The generator can run the A/C or recharge our batteries of the solar isn't keeping up. We hope to buy a boat that comes with this smaller generator already, but will add one if needed. |
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| 5) Diesel Fuel tanks Because we are keeping the diesel engines and a generator, we will need the existing diesel fuel tanks, (127 gallons on the Salina 48, 185 gallons on the Leopard 48, and 188 gallons on the Leopard 46). Some of the time these will be kept less than half full, holding perhaps 50 gallons of diesel for emergencies since most of the time we will run without any diesel usage at all for short trips and very little for midrange passages. However, when facing a long passage, or a long time away from civilization, we will top off the tanks. Sailing with just 50 gallons of diesel saves a lot of weight! On the Salina 48 it saves us 539 lbs, on the Leopard 48 is saves 945 lbs, and on the Leopard 46 it saves us 966 lbs.! This offsets the weight of the added electric propulsion system, yet still gives us plenty of range (about 360 miles motoring between the diesel engines and electric pods, more if we are willing to slow down). On short passage days, this is more than sufficient since we will likely be sailing most of it anyway. 90% of our planned passages are less than that distance so why not save the weight? |
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